Grundfos CHI 12, Installation And Operating Instructions Manual

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7
2.3 Maximum inlet pressure
The actual inlet pr pressure when the pump
is operating against a closed valve must always be
lower than the "maximum permissible operating
pressure".
2.4 Minimum inlet pressure
The minimum inlet pressure "H" in metres head
required during operation to avoid cavitation in the
pump can be calculated from the following formula:
H = p
b
x 10.2 – NPSH – H
f
– H
v
– H
s
p
b
= Barometric pressure in bar.
(Barometric pressure can be taken as
1 bar.)
In closed systems, p
b
indicates the sys-
tem pressure in bar.
NPSH = Net Positive Suction Head
(to be read from the NPSH curves
on pages 164 to 166 at the highest flow
the pump will be delivering).
H
f
= Friction loss in suction pipe in metres
head.
H
v
= Vapour pressure, see fig. G, page 167.
t
m
= liquid temperature.
H
s
= Safety margin = 0.5 metres head.
If the calculated value of H is positive, the pump can
operate with a maximum suction lift of "H" metres.
If the calculated value of H is negative, a minimum
suction head of "H" metres is required during opera-
tion of the pump to prevent cavitation.
Example:
p
b
= 1 bar.
Pump type: CHI 12, 50 Hz.
Flow rate: 12 m³/h.
NPSH (from fig. D, page 165): 3.0 metres.
H
f
= 3.0 metres head.
Liquid temperature: 90°C.
H
v
(from fig. G, page 167): 7.2 metres head.
H = p
b
x 10.2 – NPSH – H
f
– H
v
– H
s
[metres head].
H = 1 x 10.2 – 3.0 – 3.0 – 7.2 – 0.5 = –3.5 metres
head .
This means that a suction head of 3.5 metres is
required during operation.
Pressure calculated in bar: 3.5 x 0.0981 = 0.35 bar.
Pressure calculated in kPa: 3.5 x 9.81 = 34.4 kP.
2.5 Sound pressure level
The sound pressure level of the pump is lower than
70 dB(A).
3. Installation
Install the pump as shown in fig. 1, and so that ade-
quate air supply reaches the motor cooling fan.
A solid foundation should be provided for the pump,
which can be secured by bolts, if required.
Fig. 1 Installation positions
The pump sleeve can be turned 45° from the 12
o’clock position. See fig. 2.
Fig. 2 Position of discharge port
Note: If the position of the pump sleeve is to be
changed, contact Grundfos. During this procedure,
the gaskets may be damaged and the pump will leak.
The pump should be installed in such a position that
no air can accumulate in the pump sleeve. If this is
not possible, a vent screw for direct mounting in the
pump sleeve can be ordered from Grundfos, see
fig. 7.
TM
02
66
19
12
03
TM
02
6
618
10
07
45
°
45
°